The present application claims priority to Japanese Patent Application No. 2000-391867, filed Dec. 25, 2000.
1. Field of the Invention
This invention relates to novel tertiary alcohol compounds which are useful as monomers for the preparation of base resins for chemical amplification resist materials suitable for use in fine processing techniques.
2. Description of the Related Art
In recent years, increasingly finer pattern rules are required as the degree of integration and speed of LSIs become higher. Under these circumstances, far ultraviolet lithography is regarded as a promising fine processing technique of the next generation. In particular, photolithography using KrF or ArF excimer laser light as the light source is considered to be a technique indispensable for ultrafine processing to a size of 0.3 xcexcm or less, and its realization is eagerly desired.
With regard to resist materials for use in photolithography using excimer laser tight (in particular, ArF excimer laser light having a wavelength of 193 nm) as the light source, it is required that they not only have high transparency at the relevant wavelength, but also have high etching resistance which allows a reduction in film thickness, high sensitivity which does not overload the expensive materials of the optical system, and among others, high resolving power which permits fine patterns to be accurately formed. In order to meet these requirements, it is essential to develop a base resin having high transparency, high rigidity and high reactivity. However, no polymer having all of these characteristics is known at present. Thus, the existing state of the art is that no resist material suitable for practical use is available as yet.
As highly transparent resins, copolymers of acrylic acid or methacrylic acid derivatives, polymers containing an alicyclic compound derived from a norbornene derivative in the main chain, and the like are known, but none of them are satisfactory. For example, it is relatively easy to enhance the reactivity of copolymers of acrylic acid or methacrylic acid derivatives, because highly reactive monomers may be freely introduced thereinto or acid-labile units may be arbitrarily increased. However, the structure of the main chain makes it very difficult to enhance its rigidity. On the other hand, the rigidity of polymers containing an alicyclic compound in the main chain is within acceptable limits. However, their reactivity cannot be easily enhanced because, owing to the structure of the main chain, their reactivity with acid is lower than that of poly(meth)acrylates and their latitude in polymerization is low. In addition, they also have the disadvantage that, when they are applied to a substrate, their adhesion is poor because of the high hydrophobicity of the main chain. Consequently, when resist materials are prepared by using these polymers as base resins, the result will be such that they have sufficient sensitivity or resolving power, but cannot withstand etching, or they have acceptable etching resistance, but their sensitivity and resolving power are too low for practical purposes. As used herein, the term xe2x80x9c(meth)acrylatexe2x80x9d means a methacrylate or an acrylate.
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide novel tertiary alcohol compounds which are useful as monomers for the preparation of photoresist materials having high transparency and a great affinity for the substrate and hence suitable for use in photolithography using a light source comprising preferably light having a wavelength of 300 nm or less and more preferably light emitted from an ArF excimer laser.
The present inventors carried out intensive investigations with a view to accomplishing the above object, and have now found that tertiary alcohol compounds represented by the following general formula (1) can be obtained in high yield and with simplicity by employing any of the processes which will be described later, and that resins prepared by using these tertiary alcohol compounds have high transparency at the exposure wavelength of an excimer laser and resist materials using them as base resins exhibit high resolving power and good adhesion to the substrate. 
wherein R1 and R2 each independently represent a straight-chain, branched or cyclic alkyl group having 1 to 10 carbon atoms, in which some or all of the hydrogen atoms on the constituent carbon atoms may be replaced by a halogen atom or halogen atoms, or R1 and R2 may be joined together to form an aliphatic hydrocarbon ring; Z represents a straight-chain, branched or cyclic divalent organic group having 2 to 10 carbon atoms; and k is 0 or 1.
Resist materials prepared by using polymers obtained by polymerization of the tertiary alcohol compounds of the present invention are sensitive to high-energy radiation, having good adhesion to the substrate, high sensitivity, high resolving power and high etching resistance, and are useful for fine processing with electron rays or far ultraviolet radiation. In particular, since they exhibit low absorption at the exposure wavelengths of ArF and KrF excimer lasers, they can easily form fine patterns perpendicular to the substrate and are hence suitable for use as fine pattern forming materials for the manufacture of VLSI (very large scale integration).
The present invention will be more specifically described hereinbelow.
The tertiary alcohol compounds of the present invention are represented by the general formula (1).
R1 and R2 each independently represent a straight-chain, branched or cyclic alkyl group having 1 to 10 carbon atoms, in which some or all of the hydrogen atoms on the constituent carbon atoms may be replaced by a halogen atom or halogen atoms. Specific examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, bicyclo[2.2.1]heptyl, bicyclo[2.2.2]octyl, bicyclo[3.3.1]nonyl, bicyclo[4.4.0]decanyl, adamantyl, trifluoromethyl, 2,2,2-trifluoroethyl, 2,2,2-trichloroethyl, 3,3,3-trifluoropropyl and 3,3,3-trichloropropyl. Alternatively, R1 and R2 may be joined together to form an aliphatic hydrocarbon ring. Specific examples of the ring so formed include cyclobutane, cyclopentane, cyclohexane, bicyclo[2.2.1]heptane, bicyclo[2.2.2]octane, bicyclo[3.3.1]nonane, bicyclo[4.4.0]decane and adamantane. Z represents a straight-chain, branched or cyclic divalent organic group having 2 to 10 carbon atoms. Specific examples thereof include ethylene, propane-1,1-diyl, propane-1,2-diyl, propane-1,3-diyl, butane-1,1-diyl, butane-1,2-diyl, butane-1,3-diyl, butane-1,4-diyl, pentane-1,1-diyl, pentane-1,2-diyl, pentane-1,3-diyl, pentane-1,4-diyl, pentane-1,5-diyl, hexane-1,1-diyl, hexane-1,2-diyl, hexane-1,3-diyl, hexane-1,4-diyl, hexane-1,5-diyl, hexane-1,6-diyl, cyclopropane-1,1-diyl, cyclopropane-1,2-diyl, cyclobutane-1,1-diyl, cyclobutane-1,2-diyl, cyclobutane-1,3-diyl, cyclopentane-1,1-diyl, cyclopentane-1,2-diyl, cyclopentane-1,3-diyl, cyclohexane-1,1-diyl, cyclohexane-1,2-diyl, cyclohexane-1,3-diyl and cyclohexane-1,4-diyl. k is 0 or 1.
Among the tertiary alcohol compounds represented by the general formula (1), tertiary alcohol compounds represented by the following general formula (2) are especially preferred. 
wherein R3 and R4 each independently represents a straight-chain, branched or cyclic alkyl group having 1 to 6 carbon atoms, or R3 and R4 may be joined together to form an aliphatic hydrocarbon ring; and m is an integer satisfying the conditions defined by 3xe2x89xa6mxe2x89xa66.
In this formula, R3 and R4 each independently represent a straight-chain, branched or cyclic alkyl group having 1 to 6 carbon atoms. Specific examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl and cyclohexyl.
Specific examples of the tertiary alcohol compounds represented by the above general formulas (1) and (2) are as follows: 
It is believed that, in resist polymers formed by using these compounds as monomers, the tertiary alcoholic hydroxyl group which is considered to be a polar group for the development of adhesion can be located at a position remote from the main chain of the polymer through the intervention of a linker [i.e., xe2x80x94Zxe2x80x94 in formula (1)], and this permits the polymer to exhibit good adhesion to the substrate. Moreover, the lipophilicity of the polymer as a whole can be suitably regulated by choosing a compound having an appropriate number of carbon atoms with respect to k, R1, R2 and Z in the formula and using it as a raw material for the formation of the polymer. Thus, it is believed that the dissolution characteristics of the polymer can also be controlled.
The tertiary alcohol compounds of formula (1) in accordance with the present invention may be prepared, for example, according to any of the following four processes. However, it is to be understood that their preparation processes are not limited thereto. These preparation processes are specifically described below.
(A) As a first process, a desired tertiary alcohol compound (1) can be synthesized by the nucleophilic addition reaction of an organometallic reagent (3) to a ketone compound (4). 
wherein R1, R2, Z and k are as defined above, M represents Li, Na, K, MgP or ZnP, and P represents a halogen atom.
It is desirable that the organometallic reagent (3) be used in an amount of 0.5 to 2.0 moles, preferably 0.9 to 1.2 moles, per mole of the ketone compound (4). Preferred examples of the solvent include ethers such as tetrahydrofuran, diethyl ether, di-n-butyl ether and 1,4-dioxane; and hydrocarbons such as n-hexane, n-heptane, benzene, toluene, xylene and cumene. These solvents may be used alone or in admixture. The reaction temperature and the reaction time may vary widely according to the reaction conditions. For example, when a Grignard reagent (of formula (3) in which M is MgP) is used as the organometallic reagent, the reaction temperature is in the range of xe2x88x9220 to 80xc2x0 C. and preferably 0 to 50xc2x0 C. As to the reaction time, it is desirable from the viewpoint of yield to bring the reaction to completion while tracing it by gas chromatography (GC) or silica gel thin-layer chromatography (TLC). However, the reaction time usually ranges from about 0.5 to about 10 hours. The desired tertiary alcohol compound (1) can be isolated from the reaction mixture by an ordinary aqueous work-up. If necessary, the compound may further be purified according to common techniques such as distillation and chromatography.
(B) As a second process, a desired tertiary alcohol compound (1) can be synthesized by the nucleophilic addition reaction of an organometallic reagent (5) to a ketone compound (6). 
wherein R1, R2, Z, k and M are as defined above.
It is desirable that the organometallic reagent (5) be used in an amount of 1.0 to 3.0 moles, preferably 1.1 to 1.5 moles, per mole of the ketone compound (6). Preferred examples of the solvent include ethers such as tetrahydrofuran, diethyl ether, di-n-butyl ether and 1,4-dioxane; and hydrocarbons such as n-hexane, n-heptane, benzene, toluene, xylene and cumene. These solvents may be used alone or in admixture. The reaction temperature and the reaction time may vary widely according to the reaction conditions. For example, when a Grignard reagent (of formula (5) in which M is MgP) is used as the organometallic reagent, the reaction temperature is in the range of xe2x88x9220 to 80xc2x0 C. and preferably 0 to 50xc2x0 C. As to the reaction time, it is desirable from the viewpoint of yield to bring the reaction to completion while tracing it by gas chromatography (GC) or silica gel thin-layer chromatography (TLC). However, the reaction time usually ranges from about 0.5 to about 10 hours. The desired tertiary alcohol compound (1) can be isolated from the reaction mixture by an ordinary aqueous work-up. If necessary, the compound may further be purified according to common techniques such as distillation and chromatography.
(C) As a third process, a desired tertiary alcohol compound (1) can be synthesized by the nucleophilic addition reaction of organometallic reagents (5) and (7) to an ester compound (8). 
wherein R1, R2, Z, k and M are as defined above, and R5 represents an alkyl group such as methyl or ethyl.
It is desirable that the organometallic reagents (5) and (7) be used in an amount of 2.0 to 5.0 moles, preferably 2.0 to 3.0 moles, per mole of the ester compound (8). Preferred examples of the solvent include ethers such as tetrahydrofuran, diethyl ether, di-n-butyl ether and 1,4-dioxane; and hydrocarbons such as n-hexane, n-heptane, benzene, toluene, xylene and cumene. These solvents may be used alone or in admixture. The reaction temperature and the reaction time may vary widely according to the reaction conditions. For example, when Grignard reagents (of formulas (5) and (7) in which M is MgP) are used as the organometallic reagents, the reaction temperature is in the range of 0 to 100xc2x0 C. and preferably 20 to 70xc2x0 C. As to the reaction time, it is desirable from the viewpoint of yield to bring the reaction to completion while tracing it by gas chromatography (GC) or silica gel thin-layer chromatography (TLC). However, the reaction time usually ranges from about 0.5 to about 10 hours. The desired tertiary alcohol compound (1) can be isolated from the reaction mixture by an ordinary aqueous work-up. If necessary, the compound may further be purified according to common techniques such as distillation and chromatography.
(D) As a fourth process, when the desired tertiary alcohol compound is represented by the general formula (1) in which R1 and R2 are joined together to form an aliphatic hydrocarbon ring (i.e., the partial structural formula 
wherein R6 is a divalent hydrocarbon group produced when R1 and R2 are joined together to form an aliphatic hydrocarbon ring), this tertiary alcohol compound (1) can be synthesized by the nucleophilic addition reaction of an organometallic reagent (9) to an ester compound (8). 
wherein R1, R2, R5, R6, Z, k and M are as defined above.
It is desirable that the organometallic reagent (9) be used in an amount of 1.0 to 3.0 moles, preferably 1.1 to 1.5 moles, per mole of the ester compound (8). Preferred examples of the solvent include ethers such as tetrahydrofuran, diethyl ether, di-n-butyl ether and 1,4-dioxane; and hydrocarbons such as n-hexane, n-heptane, benzene, toluene, xylene and cumene. These solvents may be used alone or in admixture. The reaction temperature and the reaction time may vary widely according to the reaction conditions. For example, when a Grignard reagent (of formula (9) in which M is MgP) is used as the organometallic reagent, the reaction temperature is in the range of 0 to 100xc2x0 C. and preferably 20 to 70xc2x0 C. As to the reaction time, it is desirable from the viewpoint of yield to bring the reaction to completion while tracing it by gas chromatography (GC) or silica gel thin-layer chromatography (TLC). However, the reaction time usually ranges from about 0.5 to about 10 hours. The desired tertiary alcohol compound (1) can be isolated from the reaction mixture by an ordinary aqueous work-up. If necessary, the compound may further be purified according to common techniques such as distillation and chromatography.
When a polymer is formed by using a tertiary alcohol compound of the present invention as a monomer, it is common practice to mix the aforesaid monomer with a solvent, add a catalyst or a polymerization initiator, and subject the resulting mixture to a polymerization reaction while heating or cooling it as required. This polymerization may be carried out according to any conventional polymerization technique. Examples of the aforesaid polymerization include ring-opening metathesis polymerization, addition polymerization, and alternating copolymerization with maleic anhydride or a maleimide. In some cases, the aforesaid monomer may be copolymerized with another norbornene type monomer, a (meth)acrylate type monomer or the like.
Resist materials may generally be prepared by using the polymer obtained in the above-described manner as a base polymer and adding an organic solvent and an acid generator thereto. If necessary, a crosslinking agent, a basic compound, a dissolution inhibitor and the like may also be added thereto. Such resist materials may be prepared in the usual manner.